The covariant confined quark model is an effective quantum field approach
to hadronic interactions based on an interaction Lagrangian of hadrons
interacting with their constituent quarks [1]}.
The coupling strength of the hadrons with the constituent quarks is
determined by the so-called compositeness condition
\(Z_H = 0\)  [2]}, [3]} where \(Z_H\)  is the wave
function renormalization constant of the hadron.
Matrix elements are generated by a set of quark loop diagrams.
The ultraviolet divergences of the quark loops are regularized by
including the hadron-quark vertex functions which, in addition, describe
finite size effects due to the non-pointlike structure of hadrons.
By using Schwinger’s \(\alpha \) -representation for each local quark propagator
and integrating out the loop momenta, one
can write the resulting matrix element expression as an integral which
includes integrations over a simplex of the
\(\alpha \) -parameters and an integration over a generalized the Fock-Schwinger
proper time. By introducing an infrared cutoff on the upper limit of
the proper time one can avoid the appearance of singularities in any matrix
element. The new infrared cutoff parameter \(\lambda \)  will be taken to
have a common value for all processes.
The CCQM contains only a few model parameters: the light and heavy constituent
quark masses, the size parameters that describe the size
of the distribution of the constituent quarks inside the hadron
and unified parameter \(\lambda \) .
The model parameters are determined by a fit to available experimental data.
